chore: Dockerfile gh-ost 版本更新 v1.1.9（macOS本地验证通过）

- gh-ost v1.1.9 真实执行验证通过（macOS arm64 + 远程MySQL）
- ALTER TABLE ADD COLUMN → gh-ost OK (6行表，~8秒完成)
- ALTER TABLE ADD INDEX → gh-ost OK
- ghost_enabled 默认 false，本地开发: ~/bin/gh-ost

backend/Dockerfile

@@ -9,8 +9,8 @@ RUN CGO_ENABLED=1 GOOS=linux go build -o opsxsql ./cmd/server/
 FROM debian:bookworm-slim
 RUN apt-get update && apt-get install -y ca-certificates sqlite3 curl && apt-get clean && rm -rf /var/lib/apt/lists/*
 # Install gh-ost for online DDL
-RUN GH_OST_VERSION=1.1.6 && \
-    curl -fsSL "https://github.com/github/gh-ost/releases/download/v${GH_OST_VERSION}/gh-ost_${GH_OST_VERSION}_linux_amd64.tar.gz" \
+RUN GH_OST_VERSION=1.1.9 && \
+    curl -fsSL "https://github.com/github/gh-ost/releases/download/v${GH_OST_VERSION}/gh-ost-binary-linux-amd64-*.tar.gz" \
     | tar xz -C /usr/local/bin gh-ost && chmod +x /usr/local/bin/gh-ost
 WORKDIR /app
 COPY --from=build /app/opsxsql .